Silver costs are one third of the production costs of solar cells in photovoltaic industry [1, 2]. With decreasing
process cost and scale-up effects, reduction of silver consumption plays a more and more important role in cost
reduction. While around 150 mg silver is consumed in the front side metallization, around one third (50 mg) is
utilized for rear side solder tabs or bus bars (bb) [1]. For fingers, a high conductivity is necessary to reduce line
resistances of the metal grid and thus optimize the efficiency. Also contact resistance to the emitter plays an
important role. Thus a high silver content is unavoidable for the front metallization paste. Bus bars not necessarily
need a high silver content for low line resistances [3]. Good solderability and thus, a low oxidation degree during
firing and a high adhesion of the metal paste on the silicon surface are sufficient.
Other groups replace silver bus bars by replacing the screen printing technology with other technologies, for
example gluing [4] or tin bus bars [5]. These approaches need to have new equipment in the production line.
Our approach is based on existing screen-printing technology. We substitute the silver paste for bus bars by a
novel metal paste containing a combination of different metals with a silver content below 40%. When replacing
silver by base metals, the particle size plays an important role for the sintering process [6] and the solderability.
Additionally the oxidation progress during firing lowers the solder ability. We present a metal paste, which can
compete with present commercially available bus bar reference pastes, containing 30% less silver.